A three member panel of the U.S. 11th Circuit Court of Appeals in Atlanta issued a 51-page opinion in an appeal by the power company of an U.S. Environmental Protection Agency decision two years ago to deny a 2008 state of Alabama revision to its standard for visible emissions _ what can be seen coming from a smokestack or plant _ from 19 major sources.

"We conclude the 2011 disapproval was unauthorized by the Clean Air Act because the EPA failed to make the statutorily required error determination," the 11th Circuit stated in its opinion.

The court also affirmed the validity of the EPA's original approval of the Alabama visible emission standard and dismissed challenges to its original approval in 2008.

The court stated it rejects EPA's argument relying "on its inherent authority and this court's remand order as authorization for the 2011 disapproval."

The appeal revolves around a Clean Air Act visible emissions regulation submitted by the state of Alabama to EPA.

EPA approved the revision in 2008 after deciding the proposed regulation met the federal Clean Air Act's requirements.

EPA originally denied environmental groups' request to reconsider its ruling. But when the groups asked a second time to reconsider the decision, the EPA's new Acting Regional Administrator granted the request and in April 2009 the EPA asked the 11th Circuit Court of Appeals for permission to reconsider its ruling.

The 11th Circuit granted their request and remanded the case "on a limited basis for purposes of reconsidering the final rule under review," according to today's 11th Circuit opinion.

In 2011 the EPA disapproved the Alabama's revision. The 11th Circuit was then asked to review both the 2008 approval and 2011 disapproval.

The EPA in a 2011 statement after its disapproval said its decision "will ensure that the citizens in Alabama enjoy the health benefits and air quality protection afforded by the Clean Air Act,"

Environmental advocates had argued Alabama was too lenient on smokestack industries by allowing more instances of opaque emissions for longer periods of time. A spokesman for Alabama Power, however, has said the 2008 rule actually had tighter limits on opacity, but also included enough leeway for the utility company to deal with unexpected glitches in the pollution control equipment.

Updated at 12:08 p.m. March 6, 2013 to further define proposed change to smokestack emission standard